Modern assembly lines and the like are continually becoming increasingly complex due to the industry's efforts to further automate them and rely on sophisticated robotic devices. However, this thrust for automation has not come without problems. Many article transfer devices include powered adjustment devices and manual adjustment devices that are mounted on, and ride on a carriage for changing the orientation of a work holder in order to accommodate varying parts and transfer apparatuses. These adjustment devices present clearance problems, and may require considerable power. Further, they may require shutdown of the system for adjustment to handle new parts. Thus, designing systems for handling multiple parts of varying shapes and sizes poses numerous drawbacks.
One such article transfer device is disclosed in Applicant's U.S. Pat. No. 4,988,261. That apparatus includes an article transfer device mounted on a pair of fixed parallel tracks for power driven, longitudinal movement from one end of the tracks to another. Further included in the disclosed device is a work holder mounted upon the shuttle carriage. The work holder is independently adjustable in two types of movement relative to the shuttle carriage while requiring a single supply cable connection to the carriage. In a typical application, the transfer apparatus is positioned to extend between two machines which perform successive operations upon a workpiece. The shuttle carriage is positioned at the end of its track adjacent to the first machine, and an automotive or robotic device is employed to extract a workpiece from the first machine and load the workpiece onto the work holder of the transfer apparatus, which then drives the shuttle carriage with the workpiece to the opposite end of the transfer unit. A second automatic device then removes the workpiece from the shuttle carriage and loads it into the second machine.
Since the loading and unloading of the transfer apparatus is performed by automatic devices, it is important that the work holder of the transfer unit be precisely positioned at each end of its stroke to be in a proper orientation and alignment with the loading or unloading device. Where the production line in which the transfer apparatus is employed handles only workpieces of a single configuration, the problems of establishing the desired alignment between the transfer unit and the loading and unloading devices are simply solved by the initial setup of the unit. However, particularly in automotive related industries, present day practice requires that many production lines, particularly those which employ machines involving a large capital investment, be capable of rapid conversion from production of one part to the production of a different part. Such a changeover, in addition to the required modification of the tooling, can, and usually does, require modifications to the loading and unloading apparatus and changes to the work holder structure and its orientation upon the transfer unit, and possibly a relocation of the end positions of the shuttle carriage.
One example of such a production line is one which is employed to stamp inner door panels for automotive vehicle doors. These inner door panels are employed to mount the door latching and window operating mechanisms and are of a complex shape such that the workpiece blank passes through several successive stamping operations before it is finished. Transfer units of the general type referred to above are employed to transfer the workpiece blank from one press to the next. Typically, two or more different inner door panel configurations are required for each different model of automobile-right and left-hand configurations for two-door automobiles, and right and left front and rear door configurations for four-door automobiles.
Press lines for stamping parts of such complex shape include a series of relatively large presses fixedly mounted on the shop floor in spaced relationship to each other along a straight line. The transfer units extending between adjacent presses will have their longitudinal center lines aligned with the straight line path through the presses. Where it is intended that the line be shifted at fairly frequent intervals from production of one part to the production of a different part, to accomplish a quick change set up, the loading and unloading devices are provided with quick change modular workpiece gripping heads, and a matched set of workpiece holders are provided for the transfer unit, again with quick change couplings accommodating rapid removal and replacement upon a shuttle carriage of the transfer unit. By appropriate design, these matched pairs of workpiece grippers and workpiece holders will minimize or eliminate the necessity for reorientation or realignment of the transfer unit with its associated loading and unloading devices upon conversion from the handling of one part to the handling of another.
However, where the line must be capable of handling several different parts of differing sizes, shapes and configurations, it is frequently necessary to shift the orientation of the part between successive presses. Loading of the part upon the work holder on the shuttle carriage may, for example, be most conveniently accomplished if the work holder is inclined toward the adjacent side of the press from which it receives the part and is reversely inclined for the unloading operation at the opposite end of its stroke. Also, the geometry of a part may be such that shifting the part transversely of its path of travel between the two presses may be desirable.
Shifting of the position of the part relative to the fixed frame of the transfer apparatus during transit from one end of the apparatus to the other will normally require some power device mounted on the shuttle carriage, and the supplying of power to these actuating devices will require the coupling of an electrical cable or pneumatic hose to some point on the carriage. In that the path of travel of a typical shuttle carriage may be ten feet or more, the handling of these power cables or supply lines presents problems, since they must be connected at one end to a stationary power outlet. Guidance and handling of a single line extending from a fixed supply location to the moving carriage can easily be handled with an articulated cable guide of known construction. However, when one or more power supply lines or cables must be attached at one end to a movable shuttle carriage at locations on the carriage which are in turn movable relative to one another, a single cable guide is not sufficient. As a result, the necessity for two or more cable guides leading to the relative movable points on the shuttle present an exceedingly complex design problem.
Thus, it is an object of the present invention to provide an article transfer apparatus which is capable of rapid conversion from production of one part to the production of a different part. It is a further object of the present invention to provide such an apparatus which includes a work holder mounted upon a shuttle carriage for independent adjustable movement in at least two types of movement relative to the shuttle carriage. Still further, it is an object of the present invention to provide such an apparatus which requires no supply cable connection to the carriage and no power devices mounted on the shuttle.